CMS Pub. 100-04, ch. 15, § 20.1.6

The FS amount is determined by the FS locality, based on the POP of the ZIP Code. Use the ZIP

Code of the POP to electronically crosswalk to the appropriate FS amount. All ZIP Codes on the

ZIP Code file are urban unless identified as rural by the letter “R” or the letter “B.” Contractors

determine the FS amount as follows:

• If an urban ZIP Code is reported with a ground or air HCPCS code, the contractors

determine the amount for the service by using the FS amount for the urban base rate. To

determine the amount for mileage, multiply the number of reported miles by the urban

mileage rate.

• If a rural ZIP Code is reported with a ground HCPCS code, the contractor determines the

amount for the service by using the FS amount for the rural base rate. To determine the

amount for mileage, contractors must use the following formula:

o For services furnished on or after July 1, 2004, for rural miles 1-17, the rate

equals 1.5 times the rural ground mileage rate per mile. Therefore, multiply 1.5

times the rural mileage rate amount on the FS to derive the appropriate FS rate per

mile;

o For services furnished during the period July 1, 2004 through December 31, 2008,

for all ground miles greater than 50 (i.e., miles 51+), the FS rate equals 1.25 times

the applicable mileage rate (urban or rural). Therefore, multiply 1.25 times the

urban or rural, as appropriate, mileage rate amount on the FS to derive the

appropriate FS rate per mile.

 If a rural ZIP Code is reported with an air HCPCS code, the contractor determines the FS

amount for the service by using the FS amount for rural air base rate. To determine the

amount allowable for the mileage, multiply the number of loaded miles by the rural air

mileage rate.